On October 1, 2008, the Insurance Institute for Highway Safety (IIHS) released new ratings of child booster seats. The first of their kind, IIHS ranked boosters from those that performed as “best bets” to those that are “not recommended,” based on the seat’s ability to correctly position a vehicle’s lap and shoulder belt for booster-age children, not on their performance in simulated crash tests.

Unlike child restraints intended for smaller children that have internal harnesses, materials, and structures to restrain children and absorb crash energy, booster seats function as a positioning device to correctly place the child within the vehicle’s seatbelt system. It is the seatbelt that does the restraining, with the boosters designed to position those belts across the stronger bony structures of the hip and clavicle/collar bone rather than across the softer tissue of the abdomen and neck.

IIHS, in conjunction with the University of Michigan Transportation Research Institute (UMTRI), measured how the lap and shoulder belts fit a crash-test dummy representing the average size and weight of a six-year-old in each of 41 booster seat models.

The booster seats were evaluated using a vehicle seat with lap and shoulder belts in a range of positions based on actual vehicle measurements. Though seatbelts are highly effective at reducing injury in a crash, those that are incorrectly positioned across the lap have the potential to cause injury to the abdomen if positioned too high and if they allow children to slide under them during a crash.

Read the rest of this post on our Cars blog, including which models performed well, and advice on getting the right fit for your child.

And learn more about how to choose the right child safety seat, including the available types and features.